Article_Parameters for Mixing

7/30/2019 Article_Parameters for Mixing

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Parameters for Mixing Equipment Specifications

The following recommendations for specifying mixing equipment are offered in the interest ofassuring the owners and operators the full benefits of the expertise and competition of the mixingequipment manufacturers.

There are usually several solutions for a given application. All may work, but one is the optimumfor efficiency in achieving desired results consistent with an appropriate balance of capital andoperating costs. The specifications should contain a complete description of the process andother pertinent data and a definition of desired results with the mechanical details limited to thwhich are exclusively necessary to assure quality and performance. Thus, each mixermanufacturer is free to apply the best of his technology and designs which enhance the owner'sopportunity for the optimum solution. Therefore we recommend that the customer performs thefollowing steps.

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1. Classify the Process: In addition to general data required for almost any mixing operation,other data are required for specific processes. The various classifications are listed below anddiscussed in the accompanying article:a. Blending of Miscible Liquidsb. Solids Suspensionc. Dispersiond. Dissolvinge. Heat transferf. Crystallizationg. Chemical reactionh. Extractioni. Gas Dispersion2. Define the Objective: State explicitly what the mixer must accomplish for satisfactory results.

3. Describe the Materials to be Mixed: Give the relative percentages by weight and the sgravity and viscosity of each material. State whether the liquids are miscible and describeor gasses if any. Give the characteristics of the final mixture, including specific gravity, viscosityand temperature..

4. Outline the Mixing Cycle: State whether it is a batch or a continuous operation. If batch, gthe following data:

Batch size. Time allowed for mixing. Sequence of adding materials. Progressive changes in production characteristics Whether mixer will operate during filling or draining

If continuous, give the following data:

Gallons per minute flow rate Required retention time

5. Give Vessel Data:

Type and dimensions Shape and depth of top and bottom Mixer supports and dimensions


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Baffle details Largest opening to pass impeller Available headroom Whether a steady bearing is permissible

6. Specify type of mixer: State the type mixer required or preferred (e.g., top entering, sideentering, clamp-on portable, fixed mount portable, V-belt or gear drive, etc.).7. Specify sealing data: If a shaft seal is required, state the preferred type and material and gidata as to pressure, vacuum and temperature. In case of aside entering application, state whethethe seal is to be serviced while the vessel is under pressure.

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8. Specify Materials of Construct ion of Wetted Parts:9. Specify Motor Data: State the motor type and enclosure and the electrical requirements.10.Advise Previous Exper ience: If the mixing operation has been performed in the past, deas to the process, the equipment and the results are valuable assistance for determining theoptimum solution.Although information is sufficient for any qualified mixer manufacturer torecommend his best solution to the problem, the customer may wish to add the followingmechanical details for assurance of quality and performance.

11. The Drive Assembly: State preference for right angle or vertical arrangement. Statepreference for flange or foot mounted (flexibly coupled) motor. Do not specify the make ofcoupling unless exclusively necessary. Specify guards in accordance with OSHA standards.12. The Gear Reducer:The gear reducer should be specifically designed for mixer service withthe output shaft and bearings of sufficient size to carry the weight of the impeller shaft andimpellers, and to withstand all torsional, bending and thrust loads so that significant deflectionsare not transmitted to the gears and other

bearings. The thermal rating should not be less than the rated motor horsepower, and themechanical horsepower rating should provide the service factor suggested by the following tableas a minimum:

AGMA CLASSIFICATION

Service UniformLoad

MediumShock

Heavy Shock

Normal (10hour/day)Severe (24hour/day)

1.00 1.25 1.25 1.50 1.50 1.75

13. Reducer Bearings: All reducer bearings should be of the anti-friction type and oil or greaselubricated. No bearings should be located below the drive base. B-10 bearing life specificationsshould be related to the service life expected of the gears, as the purpose is to provide reaassurance of a given term of service before a major overhaul is required. An excessive B-specification usually forces the selection of an unnecessarily costly reducer.

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14. Lubrication: Bearings positioned outside the reducer oil supply must be grease lubricated.

Other bearings should be lubricated by a constant flow of oil through splash lubrication, an oilslinger or pump. Recommended lubricants should be in accordance with AGMA standards andavailable from local sources.15. Impeller Shafts : Impeller shafts must be able to withstand the torsional and bendingmoments inherent in the application, and to operate at or below 60% of the natural frequency ofthe system, unless equipped with an adequate stabilizing device to allow a maximum of 80%.Keyways designed to permit adjustment of the impeller may be specified, but they should bestaggered around the shaft to avoid relieving the stress on one side and causing the shaft to bo


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16. Impellers: Require only that impellers be removable and that they be attached to the shaft by

d Eastern Mixer will recommend:1. S tebal or

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2. Specify the ncorporated in

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manufactures provide protection fro ing loads imposed by the impeller

competition by c bidding.

. Specify Non-Proprietary Features: Specifying proprietary features such as the method of

a sound basis for evaluation of bids. Thus he has a greater opportunity to realize

positive means of the manufacturer's design.

Design Features, which Clevelanpecify Horsepower Output RPM or Impeller Design:The sizing of a mixer is a delicaance of horsepower, output rpm and impeller diameter and configuration. This is a maj

area for the mixer manufacturer to contribute. For example, more efficient mixing often can bechieved with lower horsepower, at a slower speed, with a larger impeller than the reverse.

The comparative initial cost depends on each manufacturer's standard line of gear reducers.The operating cost comparison is obvious.

Type of Reducer Gears: Differences in gear types can be imixer applications whereby they are reduced to a common denominator in the efficiency ofixing through the overall sizing of the equipment. Restricting the specification to a particular

restricts competition to the detriment of the customer. We provide an unbiased analy3. Specify Shaft Bearing Arrangements: Gear reducers used by qualified mixer

m torsional and bendsystem. To specify one manufacturer's method effectively reduces

ausing other manufacturers to add unnecessary cost or to refrain from

4determining oil levels, the location of oil drains, the device for lubrication, the exact distance fromthe lower bearing to the liquid level, the location of seldom changed change gears, the type ofimpeller keys, etc.; tends to describe the features of one manufacturer's equipment to theexclusion of others. This can be harmful in terms of the optimum solution as well as the cost of theequipment.

It is our sincere belief that these recommendations assure the customer the benefits of head-oncompetition andthe optimum solution for his mixing process.

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Article_Parameters for Mixing